Notification Function in APG

Good afternoon:

We have several dialogs with User Selector elements, and we wish to send an email using the Notification Function, however when creating a Collection of users from all these dialogs together (using the Collection operator), only the two first users get the e-mail, the rest are ignored.

How can we send an email to several users from different sources using only one Notification Function Task?

Regards.
Raquel.